Accumulation of alpha-synuclein has been associated with neurodegenerative disorders, such as Lewy body disease and multiple system atrophy. We previously showed that expression of wild-type human alpha-synuclein in transgenic mice results in motor and dopaminergic deficits associated with inclusion formation. To determine whether different levels of human alpha-synuclein expression from distinct promoters might result in neuropathology mimicking other synucleopathies, we compared patterns of human alpha-synuclein accumulation in the brains of transgenic mice expressing this molecule from the murine Thy-1 and platelet-derived growth factor (PDGF) promoters. In murine Thy-1-human alpha-synuclein transgenic mice, this protein accumulated in synapses and neurons throughout the brain, including the thalamus, basal ganglia, substantia nigra, and brainstem. Expression of human alpha-synuclein from the PDGF promoter resulted in accumulation in synapses of the neocortex, limbic system, and olfactory regions as well as formation of inclusion bodies in neurons in deeper layers of the neocortex. Furthermore, one of the intermediate expressor lines (line M) displayed human alpha-synuclein expression in glial cells mimicking some features of multiple system atrophy. These results show a more widespread accumulation of human alpha-synuclein in transgenic mouse brains. Taken together, these studies support the contention that human alpha-synuclein expression in transgenic mice might mimic some neuropathological alterations observed in Lewy body disease and other synucleopathies, such as multiple system atrophy.

The performances of patients with dementia of the Alzheimer type (DAT), patients with Huntington's disease (HD), and demented and nondemented patients with Parkinson's disease (PD) were compared on 2 tests of implicit memory that do not require the conscious recollection of prior study episodes: (1) a pursuit-rotor motor learning task and (2) a lexical priming test. The HD patients were found to be impaired on the motor learning but not the lexical priming task, whereas the DAT patients evidenced the opposite relationship on these tasks. The demented, but not the nondemented, PD patients were found to be impaired on both tests of implicit memory. For both the HD and PD patients, deficits on the motor learning task correlated significantly with severity of dementia but not with level of primary motor dysfunction. The noted double dissociation between HD and DAT patients indicates that different forms of implicit memory, all of which are intact in amnesia, are dependent upon distinct neuroanatomic systems. Motor skill learning may be mediated by a corticostriatal system, whereas verbal priming may depend upon the integrity of the neocortical association areas involved in the storage of semantic knowledge. The results for the PD patients suggest that the demented PD patients have endured damage to the neurologic systems subserving both motor learning and lexical priming.

In Parkinson's disease, progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SN) leads to debilitating motor dysfunction. One current therapy aims at exogenous cellular replacement of dopaminergic function by transplanting fetal midbrain cells into the striatum, the main projection area of the SN. However, results using this approach have shown variable success. It has been proposed that cellular replacement by endogenous stem/progenitor cells may be useful for therapeutic interventions in neurodegenerative diseases, including Parkinson's disease. Although it is widely accepted that progenitor cells are present in different areas of the adult CNS, it is unclear whether such cells reside in the adult SN and whether they have the potential to replace degenerating neurons. Here, we describe a population of actively dividing progenitor cells in the adult SN, which in situ give rise to new mature glial cells but not to neurons. However, after removal from the SN, these progenitor cells immediately have the potential to differentiate into neurons. Transplantation of freshly isolated SN progenitor cells into the adult hippocampus showed that these cells also have a neuronal potential under in vivo conditions. These results suggest that progenitor cells reside in the adult SN and can give rise to new neurons when exposed to appropriate environmental signals. This developmental potential of SN progenitor cells might be useful for future endogenous cell replacement strategies in Parkinson's disease.

We aimed to develop and validate a novel rating scale for multiple system atrophy (Unified Multiple System Atrophy Rating Scale-UMSARS). The scale comprises the following components: Part I, historical, 12 items; Part II, motor examination, 14 items; Part III, autonomic examination; and Part IV, global disability scale. For validation purposes, 40 MSA patients were assessed in four centers by 4 raters per center (2 senior and 2 junior raters). The raters applied the UMSARS, as well as a range of other scales, including the Unified Parkinson's Disease Rating Scale (UPDRS) and the International Cooperative Ataxia Rating Scale (ICARS). Internal consistency was high for both UMSARS-I (Crohnbach's alpha = 0.84) and UMSARS-II (Crohnbach's alpha = 0.90) sections. The interrater reliability of most of the UMSARS-I and -II items as well as of total UMSARS-I and -II subscores was substantial (k(w) = 0.6-0.8) to excellent (k(w) > 0.8). UMSARS-II correlated well with UPDRS-III and ICARS (rs > 0.8). Depending on the degree of the patient's disability, completion of the entire UMSARS took 30 to 45 minutes. Based on our findings, the UMSARS appears to be a multidimensional, reliable, and valid scale for semiquantitative clinical assessments of MSA patients.

No abstract

Multiple system atrophy (MSA) is a progressive, neurodegenerative disease characterized by parkinsonism, ataxia, autonomic dysfunction, and accumulation of ␣-synuclein (␣-syn) in oligodendrocytes. To better understand the mechanisms of neurodegeneration and the role of ␣-syn accumulation in oligodendrocytes in the pathogenesis of MSA, we generated transgenic mouse lines expressing human (h) ␣-syn under the control of the murine myelin basic protein promoter. Transgenic mice expressing high levels of h␣-syn displayed severe neurological alterations and died prematurely at 6 months of age. Furthermore, mice developed progressive accumulation of h␣-synimmunoreactive inclusions in oligodendrocytes along the axonal tracts in the brainstem, basal ganglia, cerebellum, corpus callosum, and neocortex. The inclusions also reacted with antibodies against phospho-serine (129) h␣-syn and ubiquitin, and h␣-syn was found in the detergent-insoluble fraction. In high-expresser lines, the white matter tracts displayed intense astrogliosis, myelin pallor, and decreased neurofilament immunostaining. Accumulation of h␣-syn in oligodendrocytes also leads to prominent neurodegenerative changes in the neocortex with decreased dendritic density and to loss of dopaminergic fibers in the basal ganglia. The oligodendrocytic inclusions were composed of fibrils and accompanied by mitochondrial alterations and disruption of the myelin lamina in the axons. Together, these studies support the contention that accumulation of ␣-syn in oligodendrocytes promotes neurodegeneration and recapitulates several of the key functional and neuropathological features of MSA.

Lewy bodies (LB) in the substantia nigra are a cardinal pathological feature of Parkinson's disease, but they occur in a number of neurodegenerative diseases and can be widespread in the nervous system. The characteristics, locations, and composition of LB are reviewed, with particular attention to ␣-synuclein (␣-SYN), which appears to be the major component of LB. The propensity for ␣-SYN, a presynaptic protein widely expressed in the brain, to aggregate is because of an amyloidogenic central region. The factors that favor the aggregation of ␣-SYN and mechanisms of toxicity are examined, and a mechanism through which aggregates of ␣-SYN could induce mitochondrial dysfunction and͞or release of proapoptotic molecules is proposed.

Following the discovery of inhibition of electron transport complex 1 by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which produces a parkinsonian syndrome in humans, monkeys, and mice, several laboratories have reported abnormalities of complex I and other electron transport complexes (ETCs) in various tissues from patients with Parkinson's disease (PD). Criticism of the significance of these findings in the etiology of PD has centered on whether drug treatments or the debilitation of the disease process itself produced the low ETC activities. We present results from a blinded study of platelet mitochondrial ETC activities in 18 early untreated PD patients and 18 age- and sex-matched controls and in 13 spousal controls. Lower complex I activity in platelet mitochondria of PD patients was seen in early untreated disease and thus cannot be due to debilitation or drug therapy. Home environmental factors seem an unlikely explanation for the reduced complex I activity in PD patients but have not been excluded. Complex II/III activity was also reduced by 20% in PD compared with age-/sex-matched controls. The low complex I and II/III activities in platelet mitochondria appear to be related to the etiology of PD.